For decades, scientists have had a hunch that zinc supplements could help prevent esophageal cancer, a particularly lethal malignancy that has been on the rise worldwide.

They've studied this essential nutrient in the lab, in populations around the globe, even in big clinical trials in China that gave dietary supplements to people at high risk of esophageal malignancy. The signs that zinc is protective have been intriguing, but inconsistent.

Now, however, new insights into zinc's role in gastrointestinal disorders - particularly acid-reflux disease - have renewed hopes that the pennies-a-day mineral could be therapeutic.